If you use the Tumblr app on your iPhone or iPad, you’ll want to update to the latest version. Tumblr is also advising users to change their passwords.
From the company’s staff blog:
Important security update for iPhone/iPad users
We have just released a very important security update for our iPhone and iPad apps addressing an issue that allowed passwords to be compromised in certain circumstances¹. Please download the update now.
If you’ve been using these apps, you should also update your password on Tumblr and anywhere else you may have been using the same password. It’s also good practice to use different passwords across different services by using an app like 1Password or LastPass.
Please know that we take your security very seriously and are tremendously sorry for this lapse and inconvenience.
¹ “Sniffed” in transit on certain versions of the app